Parasites and Diseases

A Field Guide


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Lung with dark infected areas. Inset: Enlarged adult worms in airway.

What causes lungworm infections?
  • A variety of roundworm parasites are known as “lungworms” (e.g., Dictyocaulus, Protostrongylus spp.).
  • Lifecycle: Adult worms are found in the lungs where they lay eggs that hatch into larvae. The larvae are coughed up, swallowed, and passed in the animals’ droppings. In some lungworms, the larvae are taken up by a snail or slug where they develop into an infective stage. The snails are then eaten by herbivores when feeding on plants. The larvae penetrate the animal’s intestines and travel to the lungs where they develop into adult worms. Other lungworms do not need a snail or slug host. The larvae develop into the infective stage on plants that are then eaten by the herbivore.

Where do lungworm infections occur?
  • Lungworms are found in bison, muskox, caribou, reindeer, and Dall sheep.
  • In Alaska a number of different lungworms occur commonly in caribou and muskox.

What are signs of a lungworm infection?
  • Animals often appear healthy.
  • Animals with severe infections may cough and have difficulty breathing, especially after running.
  • They may be generally weak and thin and have a harsh, dull hair coat.
  • When butchering, you may find adult worms or small round gray lumps of dead tissue up to ¾ inch in diameter in the lungs.
  • Lungworms are white, threadlike worms that range in size from 1/16 to 3 inches long.

How can I protect myself?
  • You cannot become infected by lungworms.

Can I eat the meat?
  • Meat from infected animals is suitable for human consumption.

Samples to collect
  • Adult worms and/or parts of lungs with cysts, droppings
  • To report an occurrence or to submit a sample for identification/analysis, contact the DWC Wildlife Disease Surveillance reporting hotline 907-328-8354, send an email to or visit your local ADF&G office.